Module 1: Transmission and Pathogenesis of Tuberculosis 

Slide 1: (Title Slide.) Self-Study Modules on Tuberculosis, 1-5. Centers for Disease Control 

and Prevention, Division of Tuberculosis Elimination, 2016. 

Slide 2: CDC Self-Study Modules on Tuberculosis, 1-5 

•	 Module 1: Transmission and Pathogenesis of TB 

•	 Module 2: Epidemiology of TB 

•	 Module 3: Targeted Testing and the Diagnosis of Latent TB Infection and TB Disease 

•	 Module 4: Treatment of Latent TB Infection and TB Disease 

•	 Module 5: Infectiousness and Infection Control 

Slide 3: (Title Slide.) Self-Study Modules on Tuberculosis: Transmission and Pathogenesis 

of Tuberculosis 

Slide 4: Module 1: Objectives 

At completion of this module, learners will be able to 

1.	 Describe the history of tuberculosis (TB). 

2.	 Explain how TB is spread (transmission). 

3.	 Define drug-resistant TB. 

4.	 Explain the difference between latent TB infection (LTBI) and TB disease. 

5.	 Explain how LTBI and TB disease develop (pathogenesis). 

6.	 Describe the classification system for TB. 

Slide 5: Module 1: Overview 

•	 History of TB 

•	 TB Transmission 

•	 Drug-Resistant TB 

•	 TB Pathogenesis 

•	 Progression from LTBI to TB disease 

•	 Sites of TB disease 

•	 TB Classification System 

•	 Case Studies 

Slide 6: (Title Slide.) History of TB 

Slide 7: History of TB (1) 

•	 TB has affected humans for millennia 

•	 Historically known by a variety of names, including: 

o	 Consumption 

o	 Wasting disease 

o	 White plague 

•	 TB was a death sentence for many 

•	 [IMAGE: Red Cross Christmas Seal Campaign vintage image circa 1919. Image 

says “The Next to Go. Fight Tuberculosis.” Image credit: National Library of 

Medicine.] 
 

 

 

 

 

 

 

 

 

 

Slide 8: History of TB (2): Scientific Discoveries in 1800s 

•	 Until mid-1800s, many believed TB was hereditary 

•	 1865 Jean Antoine-Villemin showed TB was contagious 

•	 1882 Robert Koch discovered M. tuberculosis, the bacterium that causes TB 

•	 [IMAGE: Mycobacterium tuberculosis. Image credit: Janice Haney Carr.] 

Slide 9: History of TB (3): Sanatoriums 

•	 Before TB antibiotics, many patients were sent to sanatoriums 

•	 Patients followed a regimen of bed rest, open air, and sunshine 

•	 TB patients who could not afford sanatoriums often died at home 

•	 [IMAGE: Sanatorium patients resting outside] 

Slide 10: Breakthrough in the Fight Against TB (1) 

•	 Drugs that could kill TB bacteria were discovered in 1940s and 1950s 

o	 Streptomycin (SM) discovered in 1943 

o	 Isoniazid (INH) and p-aminosalicylic acid (PAS) discovered between 1943 and 

1952 

•	 [IMAGE: TB drugs pill bottle] 

Slide 11: Breakthrough in the Fight Against TB (2) 

•	 TB death rates in U.S. began to drop dramatically 

•	 Each year, fewer people died from TB 

•	 Most TB sanatoriums in U.S. had closed by mid 1970s 

Slide 12: TB Resurgence 

•	 Increase in TB in mid 1980s 

•	 Contributing factors: 

o	 Inadequate funding for TB control programs 

o	 HIV epidemic 

o	 Increased immigration from countries where TB is common 

o	 Spread of TB in homeless shelters and correctional facilities 

o	 Increase and spread of multidrug-resistant TB 

•	 [IMAGE: March 16, 1992 Newsweek Magazine cover titled, “TB: Why It’s back. 

How We Can Protect Ourselves”] 

Slide 13: TB Prevention and Control Efforts 

•	 Increased governmental funding for TB control programs began in 1992 

•	 Number of TB cases declined from 1993 to 2014 

•	 [Image: The resurgence of TB in the mid-1980s was marked by several years of 

increasing case counts until its peak in 1992. Case counts began decreasing again in 

1993, and 2014 marked the twenty-second year of decline in the total number of TB 

cases reported in the United States since the peak of the resurgence. From 1992 until 

2002, the total number of TB cases decreased 5%–7% annually. From 2002 to 2003, 

however, the total number of TB cases decreased by only 1.4%. An unprecedented 

decrease occurred in 2009, when the total number of TB cases decreased by more 

than 10% from 2008 to 2009. In 2014, a total of 9,421 cases were reported from the 
 

 

 

 

 

 

 

 

 

 

 

 

50 states and the District of Columbia (DC). This represents a decline of 1.5% from 

2013 and 64.7% from 1992.] 

Slide 14: TB History Timeline 

•	 [IMAGE: 1865: Jean-Antoine Villemin shows that TB is contagious. 1882: Robert 

Koch discovers M. tuberculosis. 1884: First TB sanatorium established in U.S. 1943: 

Streptomycin (SM) a drug used to treat TB is discovered. 1943-1952: Two more drugs 

are discovered to treat TB. Mid-1970s: Most TB sanatoriums in U.S. closed. Mid-1980s: 

Unexpected rise in TB cases. 1993: TB cases decline due to increased funding and 

enhanced TB control efforts.] 

Slide 15: History of TB: Study Question 1.1 

•	 In what year was each of the following discoveries made? 

o	 TB was shown to be contagious - 1865 

o	 The bacterium that causes TB was discovered - 1882 

o	 The first drug that could kill TB bacteria was discovered - 1943 

Slide 16: (Title Slide.) TB Transmission 

Slide 17: TB Transmission (1) 

•	 Transmission is defined as the spread of an organism, such as M. tuberculosis, from one 

person to another. 

Slide 18: TB Transmission (2): Types of Mycobacteria 

•	 M. tuberculosis causes most TB cases in U.S. 

•	 Mycobacteria that cause TB: 

o	 M. tuberculosis 

o	 M. bovis 

o	 M. africanum 

o	 M. microti 

o	 M. canetti 

•	 Mycobacteria that do not cause TB 

o	 e.g., M. avium-complex 

•	 [IMAGE: M. tuberculosis] 

Slide 19: TB Transmission (3) 

•	 TB is spread person to person through the air via droplet nuclei 

•	 M. tuberculosis may be expelled when an infectious person: 

o	 Coughs 

o	 Speaks 

o	 Sings 

o	 Transmission occurs when another person inhales droplet nuclei 

•	 [IMAGE: Man coughing.] 

Slide 20: TB Transmission (4) 

•	 Dots in air represent droplet nuclei containing M. tuberculosis 
 

 

 

 

 

 

 

 

 

 

 

 

 

•	 [IMAGE: TB is spread person to person through the air. In this image, the dots in the 

air represent droplet nuclei containing tubercle bacilli. Droplet nuclei containing M. 

tuberculosis expel into the air from one person’s lungs and are inhaled into another 

person’s lungs.] 

Slide 21: TB Transmission (5) 

•	 Probability that TB will be transmitted depends on: 

o	 Infectiousness of the TB patient 

o	 Environment in which the exposure occurred 

o	 Frequency and duration of the exposure 

o	 Susceptibility (immune status) of the exposed individual 

•	 The best way to stop transmission is to: 

o	 Isolate infectious persons 

o	 Provide treatment to infectious persons as soon as possible 

Slide 22: TB Transmission: Study Question 1.2 

•	 What organism causes TB? 

o	 M. tuberculosis 

•	 What are four other tuberculous mycobacteria? 

o	 M. bovis, M. africanum, M. microti, and M. canetti 

Slide 23: TB Transmission Study Question 1.3 

•	 How is TB spread? 

o	 TB is spread from person to person through the air via droplet nuclei containing 

M. tuberculosis. 

Slide 24: TB Transmission Study Question 1.4 

•	 The probability that TB will be transmitted depends on what four factors? 

o	 Infectiousness of the TB patient 

o	 Environment in which exposure occurred 

o	 Frequency and duration of the exposure 

o	 Susceptibility (immune status) of the exposed individual 

Slide 25: (Title Slide.) Drug-Resistant TB 

Slide 26: Drug-Resistant TB (1)

•	 Caused by M. tuberculosis organisms resistant to at least one TB treatment drug 

•	 Resistant means drugs can no longer kill the bacteria 

Slide 27: Drug-Resistant TB (2) 

Mono-resistant Resistant to any one TB treatment drug 

Poly-resistant Resistant to at least any 2 TB drugs (but not 

both isoniazid and rifampin) 
 

 

 

 

 

 

 

 

 

 

 

Multidrugresistant 

(MDR TB) 

Resistant to at least isoniazid and rifampin, 

the 2 best first-line TB treatment drugs 

Extensively 

drug-resistant 

(XDR TB) 

Resistant to isoniazid and rifampin, PLUS 

resistant to any fluoroquinolone AND at least 

1 of the 3 injectable anti-TB drugs (e.g., 

amikacin, kanamycin, or capreomycin) 

Slide 28: Drug-Resistant TB (3) 

Primary 

Resistance 

Caused by person-to-person transmission of 

drug-resistant organisms 

Secondary 

Resistance 

(acquired) 

Develops during TB treatment: 

- Patient was not treated with an 

appropriate regimen 

OR 

- Patient did not follow treatment 

regimen as prescribed 

Slide 29: Drug-resistant TB: Study Question 1.5 

•	 What is drug-resistant TB? 

o	 Drug-resistant TB is caused by M. tuberculosis organisms that are resistant to at 

least one anti-TB drug. 

o	 Drug-resistant TB can be difficult to treat. 

Slide 30: Drug-resistant TB: Study Question 1.6 

•	 What is the difference between primary and secondary drug resistance? 

o	 Primary resistance is caused by person-to-person transmission of drug-resistant 

organisms. 

o	 Secondary resistance develops during TB treatment. Either the patient was not 

treated with the right TB drugs or the patient did not follow the prescribed 

treatment regimen. 

Slide 31: (Title slide.) TB Pathogenesis 

Slide 32: TB Pathogenesis (1) 

• Pathogenesis is defined as the way an infection or disease develops in the body. 

Slide 33: TB Pathogenesis (2): Latent TB Infection (LTBI) 

•	 LTBI occurs when tubercle bacilli are in the body, but the immune system is keeping 

them under control 

•	 LTBI is detected by the Mantoux tuberculin skin test (TST) or by an interferon-gamma 

release assay (IGRA), such as: 

o	 QuantiFERON®-TB Gold In-Tube (QFT-GIT) 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

o	 T-Spot®.TB test (T-SPOT) 

•	 People with LTBI are NOT infectious 

Slide 34: TB Pathogenesis (3): TB Disease 

•	 TB disease develops when the immune system cannot keep tubercle bacilli under control 

o May develop very soon after infection or many years after infection 

•	 About 10% of all people with normal immune systems who have LTBI will develop TB 

disease at some point in their lives 

•	 People with TB disease are often infectious 

Slide 35: TB Pathogenesis (4) 

•	 Droplet nuclei containing tubercle bacilli are inhaled, enter the lungs, and travel to small 

air sacs (alveoli) 

•	 [Image: Tubercle bacilli are inhaled and enter the lungs.] 

Slide 36: TB Pathogenesis (5) 

•	 Tubercle bacilli multiply in alveoli, where infection begins 

•	 [IMAGE: Section of the bronchiole, alveoli, and tubercle bacilli within the alveoli.] 

Slide 37: TB Pathogenesis (6) 

•	 A small number of tubercle bacilli enter bloodstream and spread throughout body 

•	 [IMAGE: Anatomical view showing the brain, lung, kidney, and bones.] 

Slide 38: TB Pathogenesis (7): LTBI 

•	 Within 2 to 8 weeks the immune system produces special immune cells called
 

macrophages that surround the tubercle bacilli
 

•	 These cells form a barrier shell that keeps the bacilli contained and under control (LTBI) 

•	 [IMAGE: Close view of the alveoli, where special immune cells form a barrier shell 

around the tubercle bacilli. In this example, the bacilli are in the lungs.] 

Slide 39: TB Pathogenesis (8): TB Disease 

•	 If the immune system CANNOT keep tubercle bacilli under control, bacilli begin to 

multiply rapidly and cause TB disease 

•	 This process can occur in different places in the body 

•	 [IMAGE: Close view of the alveoli, where the special immune cells break down and 

the tubercle bacilli escapes. In this example, TB disease develops in the lungs.] 

Slide 40: LTBI vs. TB Disease (1) 

Person with LTBI Person with TB Disease 

(in the lungs) 

• Has a small number of TB 

bacteria in his or her body that 

are alive, but under control 

• Has a large number of active TB 

bacteria in his or her body 
 

 

 

 

 

 

 

 

 

 

 

 

 

• Cannot spread TB bacteria to 

others 

• May spread TB bacteria to others 

• Does not feel sick, but may 

become sick if the bacteria 

become active in his or her body 

• May feel sick and may have 

symptoms such as cough, fever, or 

weight loss 

• TST or IGRA results usually 

positive 

• TST or IGRA results usually 

positive 

• Chest x-ray usually normal • Chest x-ray usually abnormal 

Slide 41: LTBI vs. TB Disease (2) 

Person with LTBI Person with TB Disease 

(in the lungs) 

• Sputum smears and cultures 

negative 

• Sputum smears and cultures may 

be positive 

• Should consider treatment for 

LTBI to prevent TB disease 

• Needs treatment for TB disease 

• Does not require respiratory 

isolation 

• May require respiratory isolation 

• Not a case of TB • A case of TB 

Slide 42: TB Pathogenesis Study Question 1.7 

•	 When a person inhales droplet nuclei containing M. tuberculosis, where do the droplet 

nuclei go? 

o	 Most of the larger droplet nuclei become lodged in the upper respiratory tract, 

where infection is unlikely to develop 

o	 However, droplet nuclei may reach the small air sacs of the lung (the alveoli), 

where infection may begin 

Slide 43: TB Pathogenesis Study Question 1.8 

•	 After the tubercle bacilli reach the small air sacs of the lung (the alveoli), what happens 

to the tubercle bacilli? 

o	 Tubercle bacilli multiply in alveoli and some enter the lymph nodes and 

bloodstream and spread throughout the body 

o	 Bacilli may reach any part of the body 

o	 Within 2 to 8 weeks, the immune system usually intervenes, halting multiplication 

and preventing further spread 

Slide 44: TB Pathogenesis Study Question 1.9 

•	 In people with LTBI (but not TB disease), how does the immune system keep the
 

tubercle bacilli under control?
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

o	 The immune system produces special immune cells that surround the tubercle 

bacilli. The cells form a shell that keeps the bacilli contained and under control. 

Slide 45: TB Pathogenesis Study Question 1.10 

•	 How is LTBI detected? 

o	 LTBI is detected by the Mantoux tuberculin skin test (TST) or blood tests such as 

interferon-gamma release assays (IGRAs), which include the QuantiFERON®-TB 

Gold In-tube (QFT-GIT) or the T-SPOT®.TB test (T-SPOT). 

Slide 46: TB Pathogenesis Study Question 1.11 

•	 What are the major similarities and differences between LTBI and TB disease? List 

characteristics of each. 

Person with LTBI Person with TB Disease 

(in the lungs) 

• Has a small number of TB 

bacteria in his or her body that 

are alive, but under control 

• Has a large number of active TB 

bacteria in his or her body 

• Cannot spread TB bacteria to 

others 

• May spread TB bacteria to others 

• Does not feel sick, but may 

become sick if the bacteria 

become active in his or her body 

• May feel sick and may have 

symptoms such as cough, fever, or 

weight loss 

• TST or IGRA results usually 

positive 

• TST or IGRA results usually 

positive 

• Chest x-ray usually normal • Chest x-ray usually abnormal 

• Sputum smears and cultures 

negative 

• Sputum smears and cultures may 

be positive 

• Should consider treatment for 

LTBI to prevent TB disease 

• Needs treatment for TB disease 

• Does not require respiratory 

isolation 

• May require respiratory isolation 

• Not a case of TB • A case of TB 

Slide 47: TB Pathogenesis Study Question 1.12 

•	 What happens if the immune system cannot keep the tubercle bacilli under control and 

the bacilli begin to multiply rapidly? 

o	 When this happens, TB disease develops. The risk that TB disease will develop is 

higher for some people than for others. 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Slide 48: (Title Slide.) TB Pathogenesis: Progression from LTBI to TB Disease 

Slide 49: Progression to TB Disease (1) 

•	 Risk of developing TB disease is highest the first 2 years after infection 

•	 People with LTBI can be given treatment to prevent them from developing TB disease 

•	 Detecting TB infection early and providing treatment helps prevent new cases of TB 

disease 

Slide 50: Progression to TB Disease (2) 

•	 Some conditions increase probability of LTBI progressing to TB disease 

o	 Infection with HIV 

o	 History of untreated or inadequately treated TB disease 

o	 Recent TB infection (within the past 2 years) 

o	 Immunosuppressive therapy such as tumor necrosis factor-alpha (TNF) 

antagonists, systemic corticosteroids, or immunosuppressive drug therapy 

following organ transplantation 

o	 Abusing drugs or alcohol or smoking cigarettes 

o	 Silicosis 

o	 Diabetes mellitus 

o	 Chronic renal failure 

o	 Certain types of cancer (e.g., leukemia, cancer of the head, neck, or lung) 

o	 Certain intestinal conditions 

o	 Low body weight 

Slide 51: Progression to TB Disease (3) 

•	 [IMAGE: Flowchart. People who are exposed to TB may or may not develop TB 

infection. People with LTBI may or may not develop TB disease.] 

Slide 52: Progression to TB Disease (4): TB and HIV 

•	 In an HIV-infected person, TB can develop in one of two ways: 

o	 Person with LTBI becomes infected with HIV and then develops TB disease as 

the immune system is weakened 

o	 Person with HIV infection becomes infected with M. tuberculosis and then 

rapidly develops TB disease 

•	 [IMAGE: Poster that reads, “TB/ HIV. Double Trouble. People with HIV infection 

face greater risk of also developing TB. Don’t take chances. Get tested.” Image 

credit: Mississippi State Department of Health.] 

Slide 53: Progression to TB Disease (5): TB and HIV 

•	 People who are infected with both M. tuberculosis and HIV are much more likely to 

develop TB disease 

•	 [IMAGE: For persons with TB infection and no risk factors, the risk is about 5% in 

the first 2 years after infection and about 10% over a lifetime. For people with TB 

infection and diabetes, the risk is 3 times greater, or about 30% over a lifetime. For 

people with TB infection and HIV infection (not on HIV treatment) the risk is about 

7% to 10% PER YEAR, a very large risk over a lifetime.) 
 

 

 

 

 

 

 

 

 

 

 

 

 

Slide 54: Progression to TB Disease: Study Question 1.13 

•	 What percentage of people who have LTBI (but not HIV infection) usually develop TB 

disease? 

o About 10% of all people with LTBI will develop TB disease at some point 

•	 In U.S., about 5% of recently infected will develop TB disease in first year 

or two after infection 

•	 Additional 5% will develop disease later in life 

o Remaining 90% will remain free of disease for the rest of their lives 

Slide 55: Progression to TB Disease: Study Question 1.14 

• What conditions appear to increase the risk that LTBI will progress to TB disease? 

o	 Infection with HIV 

o	 History of untreated or inadequately treated TB disease 

o	 Recent TB infection (within the past 2 years) 

o	 Immunosuppressive therapy such as tumor necrosis factor-alpha (TNF) 

antagonists, systemic corticosteroids, or immunosuppressive drug therapy 

following organ transplantation 

o	 Abusing drugs or alcohol or smoking cigarettes 

o	 Silicosis 

o	 Diabetes mellitus 

o	 Chronic renal failure 

o	 Certain types of cancer (e.g., leukemia, cancer of the head, neck, or lung) 

o	 Certain intestinal conditions 

o	 Low body weight 

Slide 56: Progression to TB Disease: Study Question 1.15 

•	 How does being infected with both M. tuberculosis and HIV affect the risk for TB 

disease?
 

o	 Much more likely to develop TB disease 

o	 Risk of developing TB disease is 7% to 10% EACH YEAR (if HIV is not being 

treated) 

o	 In an HIV-infected person, TB disease can develop in two ways: 

1.	 Person with LTBI becomes infected with HIV and then develops TB 

disease as the immune system is weakened 

2.	 Person with HIV infection becomes infected with M. tuberculosis and then 

rapidly develops TB disease 

Slide 57: (Title Slide.) TB Pathogenesis: Sites of TB Disease 

Slide 58: Sites of TB Disease (1) 

•	 Bacilli may reach any part of the body, but common sites include: brain, larynx, lungs, 

kidneys, lymph nodes, spine, and bones. 

•	 [IMAGE: Anatomical view showing the brain, larynx, lung, kidney, lymph nodes, 

pleura, spine, and bones.] 

Slide 59: Sites of TB Disease (2) 
 

 

 

 

 

 

 

 

 

 

 

Location Frequency 

Pulmonary TB Lungs Most TB cases are 

pulmonary 

Extrapulmonary TB Places other than lungs 

such as: 

 Larynx 

 Lymph nodes 

 Pleura 

 Brain 

 Kidneys 

 Bones and joints 

Found more often in: 

- HIV-infected or 

other immunosuppressed 

persons 

- Young children 

Disseminated TB Carried to all parts of 

body, through 

bloodstream 

Rare 

Slide 60: Sites for TB Study Question 1.16 

• What part of the body is the most common site for TB disease? 

o Lungs are the most common site 

• What are some other common sites? 

o Larynx 

o Lymph nodes 

o Pleura (membrane around the lungs) 

o Brain 

o Kidneys 

o Bones and joints 

Slide 61: (Title Slide.) TB Pathogenesis: TB Classification System 

Slide 62: TB Classification System (1)

• Based on pathogenesis of TB 

Class Type Description 

0 No TB 

exposure 

Not infected 

No history of TB exposure 

Negative result to a TST or to an 

IGRA 

1 TB exposure 

No evidence 

of infection 

History of TB exposure 

Negative result to a TST or an IGRA 

(done at least 8 to 10 weeks after 

exposure) 
 

 

 

 

 

 

 

 

 

2 TB infection 

No TB 

disease 

Positive result to a TST or to an IGRA 

Negative smears, molecular tests, and 

cultures 

No clinical or x-ray evidence of active 

TB disease 

Slide 63: TB Classification System (2) 

• Based on pathogenesis of TB 

Class Type Description 

3 TB, 

clinically 

active 

Positive culture for M. tuberculosis OR 

Positive result to a TST or to an IGRA, 

and clinical, bacteriological, or x-ray 

evidence of current active TB disease 

4 Previous TB 

disease 

(not 

clinically 

active) 

Medical history of TB disease 

Abnormal but stable x-ray findings 

Positive result to a TST or to an IGRA 

Negative smears, molecular tests, and 

cultures (if done) 

No clinical or x-ray evidence of active 

TB disease 

5 TB 

suspected 

Signs and symptoms of TB disease, but 

diagnostic evaluation not complete 

Slide 64: TB Classification System Study Question 1.17 

•	 What is the classification system for TB based on? What is it used for? 

o	 The current classification system is based on the pathogenesis of TB. Many 

health departments and private health care providers use this system when 

describing patients. 

Slide 65: (Title Slide.) Case Studies 

Slide 66: Module 1: Case Study 1.1 (1) 

•	 A 30-year-old man visits the health department for a TST because he is required to have 

one before starting his new job as a health care worker. He has an 18 mm positive 

reaction to the TST. He has no symptoms of TB, and his chest x-ray findings are normal. 

Slide 67: Module 1: Case Study 1.1 (2) 

•	 Should this be considered a case of TB? 
 

 

 

 

 

 

 

 

 

 

 

o	 No. The man described above has LTBI. He has an 18 mm positive reaction to the 

TST, but no evidence of TB disease. Therefore, this is not a case of TB. 

•	 Should this man be considered infectious? 

o	 No, he should not be considered infectious. This man has LTBI, not TB disease. 

People with TB infection and no evidence of TB disease are not infectious. 

Slide 68: Module 1: Case Study 1.2 (1) 

•	 A 45-year-old woman is referred to the health department by her private physician 

because she was found to have LTBI as part of an employee testing program. She is 

overweight, with high blood pressure. Upon further questioning, she reports that she has 

injected illegal drugs in the past, but has never been tested for HIV infection. 

Slide 69: Module 1: Case Study 1.2 (2) 

•	 What conditions does this woman have that increase the risk that she will develop TB 

disease? 

o	 Drug abuse increases the risk that LTBI will progress to TB disease. This woman 

may also be at risk for HIV infection because of her injection drug use. HIV is the 

strongest known risk factor for developing TB disease. This woman should be 

offered HIV counseling, testing, and referral. Overweight and high blood pressure 

are NOT risk factors for TB disease.